Broken lock - who should pay?

[Mark Oliver]

My new tenants moved in 5 days ago. On the first day, they said the AC was not working well enough. On the 3rd day, they said there was an electrical issue (when the light switch in the bedroom is turned off all the electrical outlets turn off in the basement too). Today (on the 5th day) they said the lock on the sliding door leading to the back yard is broken. This seems like a lot of complaints in a short period of time. What do you think? And who should pay? 
For the AC, I quickly provided them with 2 portable AC units for the upstairs rooms that they said were "unbearable". Though the previous owners said the AC was fine, and myself and the realtor knew it was fine most of the summer. I agreed to pay their first month's electricity and look into making the AC better once we know the issue. I am getting an electrician out to see what the issue is with the electrical. But the back sliding door. Seriously. This was working fine when they started renting. I'd like to make sure their first week goes well, but OMG, this is eating into any profit I might get and is starting to annoy me. Advice?